Studying the aging of Laponite suspensions using extensional rheology

Abstract

The effect of aging on the break-up dynamics of Laponite suspensions was studied in an extensional geometry. It was found that samples of increased age undergo stronger necking at the midpoint. The thinning of samples, driven purely by motion of the plates, was compared with standard shear rheology to understand how the dynamics are related to the sample properties. The Laponite suspensions exhibit a growing stress overshoot with monotonically decreasing yield strain as they age. However, it is shown that the thinning curves in extension are only a good indicator of the sample’s static yield stress, being insensitive to its yield strain. These measurements suggest that following an initial linear visco-elastic regime, samples accumulate significant plastic deformations prior to the complete yielding of the sample. The implications of this for the importance of assessing changes to the ductile—brittle nature of samples are also discussed. Graphical abstract

Physico‐Chemical Properties of Laponite®/Polyethylene‐oxide Based Composites

“…where N A is Avogadro's number,R g is the hydrodynamic radius of the PEO chains (R g � 0.022M w 0.583 Recent rheological experiments with Lap suspensions (C Lap = 3, 3.5 and 4 %, pH = 10) demonstrated that after an initial linear visco-elastic regime, the samples accumulate significant plastic deformations prior to the complete yielding of the sample. [58] During the aging the samples became slightly more brittle and the sample with high Lap concentration exhibited shear bands.…”